Seeing as this topic doesn't seem to have been updated for a while, just a heads up on a couple of places that we found and enjoyed. For dinner although probably one of the more expensive places, we found the Christos Taverna, (first taverna at the end of the harbour) to be excellent for fresh fish. Friendly service and a nice breeze off the sea to cool you down after a long day on the beach.
The second one we found possibly for lunch, was a kebab house for which I have forgotten the name. However, coming away from the harbour going east, it's just past the Sofia restaurant on the same side. Small place but great lamb or pork souvlakia (two skewers), served with fries, salad and tzaziki all for €5.
I'd also agree with what Susan told us regarding the first taverna on the left in Mirthios, which has marvellous views over the bay of Plakias and good food. This one is good at lunchtime or for dinner.
Happy eating
Martyn & Svetlana